Dimpling tool



J. G. l-luRsi DIMPLING Tool..

March 28, 1944.

atented aro @dei '2,344,944 numana Toor.

James4 G. Hurst. Los Angeles, Calif., assignor to Douglas Aircraft Company, Inc., Santa Monica.

Calif.

Applicationeptember 7, 1942, Serial No. 457,633

` 11 claims. v (cl. 153-21) 'rhisinvention "relates to the art of dimming rivet holes in relatively thin and resilient metal sheets preparatory to driving ush rivets dr of otherwise forming such sheets adjacent apertures therein between a driving die and a bucking die or anvil. Speciilcally, the invention is contained in a dimpling tool adapted for use in closely restrictedV areas whereit is diiilcult or impossible to employ twomen, one driving the dimple and one bucking the impulses of the tool. L

In certain industries, such as thev airplaneindpstry, metal sheets are secured together by ilush riveted joints so that a smooth exterior surface may be obtained. It is found that the most satisfactory joint of this type is obtained by form- `ing a frusta-conicalshaped recess surrounding each rivet hole in the sheets to be joined so that the head of .a rivet oi the countersunk type seat'therein. This operation will be hereinafter referred to as dimpling and is not to be confused with lthe usual type of countersinking.

which is formed by cutting away suihcient metal of one or more sheets to receive all or part of a rivet head. The method of duid control for rivet guns and other impact tools is old in the art and therefore it is understood that this invention deals primarily with improvements in the gun mechanism. Y

It'is the principal object of this invention to provide a simple eiilcient means for forming dimples in relatively thin and resilient metal sheets preparatory to driving ush rivets.

.Another object is to provide a dimpling tool which will save both time and energy in its ability to form dimples in restricted areas Where it is difflcult to employ two men.

Another object is to provide a dimpling and bucking tool in one unit.

Another object is to provide a simple means for which may be easily -fastened to a part of the gun by the operator from the reverse side ofthe sheet or sheets to be dimpled. A 1

Another object is to provide a dimpling gun having a hammer and anvil in the form of a male andiemale die which co-act to f orm a perfect dimple.

Still another cbiect .of this invention is to pro- 5 5 The forward end'of the valve stem `I5 protrude; l

vide an automatic centering device for the `coacting dies.

Further objects and advantages of the invention will be brought out in the following description taken in connection with the accompanying drawings and appended claims.

Referring now to the drawings:

Figure 1 is a` longitudinal view in section of a dimpling gun embodying the invention, showing the position which the parts assume when the striker piston is at the end of its rearward stroke.

Figure 2 is a longitudinal view in section oi the dimpling gun of Figure 1 showing the striker piston thereol in the striking position. Y Figure 3 is an enlarged longitudinal fragmen tary view in section of the dimpling gun of Figue i showing the rst step inthe dimpling oi a s ee Figure is an enlarged longitudinal fragmentary view in section similar to Figure 3 but showing the second or driving step in the forming of the dimple.

Figure 5 is an enlarged longitudinal fragmen tary view in section similar to Figure 4 but showing the finished dimple, and

Figure 6 is an enlarged plan view of the completely dimpled hole.

Percussive tools and the Vcontrol .thereof are well known in the art. ForL example, Patent Number 2,101,159 shows pneumatic gun and its .controlling mechanism in. detail. The present inventionv is an improvement on such a tool and accordingly the description and drawings herein do not repeat the details of these known desure supply line and is provided 'with an inlet duct I2 leading from the point vof connection to the interior of the cylinder lll. A valve i3 has a stem l5 which is slidable in a bore i6 in the grip handle and has a head Il mounted thereon and engageable with a seat I8 to therebycontrol the passage of iluid in the duct I2. A spring 2l is interposed between the valv head i1 and a threaded plug 22Dto hold the valve-yeldably against its seat IB. From the valve, a contnua` tion of the duct l2A leads directly to the cylinder and delivers live motive uid to the cylinder during one phase oi the guns operation `and serves as an exhaust during another phase.

from the grlp'handle and bears againsta trigger 23 pivotally carried by a pin 24 s et in a slotted ear 25 formed on the handle I I.

To form the rear closure for the cylinder lli a hub-like extension 2l on a knurled hand wheel 21 is held rotatably in a central bore of a screw type plug 28, the plug 28 having threaded engagement with the left end of the cylinder I0. An annularl groove 26a in thehub 2B receives a set` screw 29 set in the plug 23 so that the hand wheel may thereby be restrained from axial movement with respect to the plug 28 and cylinder I0. A

central bore through the hand wheel hub 2B allows a tension rod 3l to be Apassed therethrough. `A conicaliy shaped head 32 on the left end of rod 30 fits within a countersunk hole 3| in the wheel 21, preventing rightward axial movement of ther-od vin the cylinderV Ill. A-key 33 in keyway slots in the head 32 and wheel 21 prevents relative rota.- `tion of the rod 3|! and wheel 21. The hole 3I is closed by a threaded plug 34 which prevents lefti ward axial movement' ofthe rod in the cylinder I 0.

f When the tension rod is'assembled to the dimpling Yaclarar.;

. be dimpled corresponding to the diameter of the rivet used.- This self-'centering movement is' accomplished by 'the rounded portion `3Iib on the tension rod extremity which .cooperates with the recessed portion 5I of the anvil member 4 9. The threads on the tension rodare -adapted to cooperate with those'pr'ovided in the anvil member so that the latter may be threaded thereon from the opposite side of the sheet 56. It will be noted from the drawings (Figures 3, 4 and L5) that a smooth portion of the threaded tension rod engages a similar smooth portion of the anvil member and the bearing or work engaging surface 54' f gun a threaded portion 3Ia`and a rounded portion 33h extend 'forwardly therefrom.

A piston chamber 35 is provided in the cylinder I0 and a striker piston 3 3 reciprocates therein. A central bore in the striker piston enables the tension rod to be passed therethrough. The striker piston is adapted to strike a head 31 on a hammer member or die 38 which is also provided with a central bore 33. 'I'he forward portion of the hammer member 33 is formed in the shape of a conical frustum having an'included angle of substantially 100.i -fl'he hammer Vmember closes the iront portion of the cylinder and is maintained in-a slidable relation thereto by reason of its being supported in a central bore 40 of a cylinder 4I. .The cylinder 4I and cylinder III constitute a housing for the hammer 38 and associated parts.

An annular stop shoulder 4211s provided in the forward portion of the cylinder piston chamber 35 against which rests'a shock ring 43 so as to ber at 58. 'I hus the'anvil member is solidly. supported at this point thereby reducing some of the strain which -mlght otherwise be concentrated upon the threads 30d. The knurled adistment wheel 21 on the rear. extremity of the gun is turned, rotating the tension rod, the threaded end of which lsthreaded into the .anvil member. 43, so that the sheet of metal, is securely clamped between the bearing surface 52 of the anvil memof the cylinderll. The trigger 231s depressed, thereby-unseating the valve head I1 from the valve seat I8.

.The released charge of fluid causes the strike piston 36 to deliver a heavy blow` to the head 31 of the hammer member 38. The i'rustum shaped nose of .the hammer member is driven against the sheet and forces it to assume thel configurationof the recess 5I inthe anvil member as shown in Figures 2 an'd 50i ,the drawings. After a blow has been delivered to the hmmer'member 38 the striker piston 3S is returned to its voriginal position upon release of the triggerv 23 by the application of iluid pressure to the forward side of the striker piston through a fluid passage 60 in the manner .described in the abovementioned Patent Number 2,101,159.

- dimpled. With this hand wheel a quick adjust-f limit the iorward`travelof the hammer head. A.

spring 44 is wrapped around the hammer member 33 and is interposed between the forward 'face of the hammer head 31 and the forward portionof a coxmterbore 45 in the cylinder 4I. An outwardlyA projecting annular ilange 46 on the 'cylinder 4| allows the cylinder 4I Vto be held securely to the end of the cylinder I l by a retaining cap 41 which isV threaded thereon. lA gasket 48 is inserted between the cap 41 and iiange l46. to form an airtight joint. Thus when Viluid isdirected against the hammer member-to returnit to its original position there will be no leakage past this joint topreventthis return movement. A

The -central bore through the striker piston 36 4and the hammer member 33 enables the tension rod which extends therethrough 'to be. rotated. freely sothat after the threaded end of the rod has been passed through lthe sheet to be inentis'provided which enables theoperator to -spin the centering rod into the anvil member-so that a few turnsof the hand wheel will draw the anvil member tightly dimpled.

'.It will also be `noted'from the drawings, Figures 3, 4 and 5, that the face' 52 of the anvil member is provided with a slightly beveled surface. beveled surface terminates at the periphery ofthe recessed portion 5I. In this against the sheet to be manner the'at surface is adapted to provide a perfect matching of the pressure areas on both the outer end face of the cylinder 4I and the anvil member 49 so that there is no possibility4 of disguratiomof the sheet being dimpled by sharp edges on the anvil member. Thus, each blow oi the hammer is guided and delivered directly, to thecenter of the recess lil. AIn addition each blow of the hammer member is backed by a be rapidly threaded thereon. The anvil member fsolidlysupported surface, thus precluding any possibility of displacement of the anvil member isprovided witha recess 5I up'on its slightly vbev- 55 with resulting irregularity in the dimples so eled bearing or operative face i2 which recess'has an included 'angle of substantially 100correvspending to the nose of the hammer member 33.

The 100 angle mentioned hereinabove corre- Sponds to a standard 100? rivet commonly used.

However, it is to Ybe understood the angle may be `formed.

Iclaim: 1. In aV tool for die prising apertured plates. the combination of: a

tool housing having at one end a work engaging face; acentrally bored die slidably projectible from the housing.: a bucking die independent of,

the work article for cooperating with said vprojectible die, a tension roddimensioned to pass through an aperture in the plates, said tension The knurled hand wheel 21 is provided on the forming work articles comi rod being disposed in the bore of said projectible die and securable to said bucking die, and having an end thrust -eng-agement with said housing preventing movement of said rod toward said work engaging iace; and means associated with said rod for placing it under tension to draw said bucking die, when, secured to said rod, toward said housing to clamp the work article between said work engaging face and bucking die; and means for applying a force to project the die outl0 wardly relative to the housing into forming contact with the work article while the work article is thus clamped.

2. In e. tool for forming work articles comprising apertured plates, the combination of: a tool housing having at one end ya work engaging tace ,and a forming tool projectible from the housing; an anvil independent of the work article for cooperating with said tool, said anvil having s. 'rho combination donned in oioim 4' in which said means for applying a torce to said projectible die comprises a piston hammerl reclprocatively movable within said barrel and pneumatic means for effecting .said reclprocative movements, and in which said proiectible die has a hammer head at its inner end and in addition thereto, a coiled compression spring seated between vsaid hammer head and the outer end portion oi said barrel for'retraction of said proiectible die after each outward movement of said hammer.

'1. The combination defined in claim 2 and in` addition thereto: means for preventing movement of said rod toward the other end of said housing.

8.v The combination defined in claim 4 in which said worle engaging face is normal to the axis oi' the tool and the operative face oi' said bucking die outside of the forming surface ilares conicaliy at a slight angle away from a plane normal at least one threaded bore: and a tension rod t0 the axis 0! the tool.

having and end thrust engagement with said housing preventing movement toward said work engaging face, said tension rod being dimensioned to pass through -one of the plate apertures and 9. In a tool for die forming work articles comprising apertured plates, the combination-oi: a barrel having at one Aend an annular work engaging face; a centrally bored die pro being threaded for engagement with said thread- 25 from Said barrel Centrally 0f said face; a bucking ed bore whereby the anvil and rod may be relatively rotated to clamp the work article between said work engaging face and said anvil; and means for applying a force to project the tool die independent of the work article for cooperating with said projectible die, said bucking die having a threaded bore; a tension rod dimensioned to pass through an aperture in the plates,

from the housingA into forming contact with the said tension rod being disposed in and projecting Vwork article while the work is clamped.

3. 'I'he combination dened in claim 2, in which said rod is rotatably mounted in said housing, and in addition thereto; means on said housing` for rotating said rod.

4. In a tool for die forming work articles com, prising apertured plates, the combination of: a barrel having at one end an annular wor/k engaging tace and acentrally bored die projectible from Q,

at each end from the bore of said prolectible die. and threaded at its outer end for engagement l with said threaded bore whereby the bucking die and rod may be relatively rotated to clamp the `'work article between said work engaging race and said bucking die; means for applying a force to project the projectible die from the barrel into forming contact with tl work article while the work is thus clamped; and-a head secured to the said barrel centrally or said face; a bucking die' 4o inner end 0f Said rod fol' end thrust engagement 'independent of the work article for cooperating with said projectible die, saidbucking die having a threaded bore: a tension rod dimensioned to pass through an aperture in the plate, said tension rod being disposed inand projecting at 5 each end from the bore of said projectible die, having an end thrust engagement with said barrel preventing movement toward said work engaging-iace and threaded at the outer end for um engagement with said threaded bore whereby the vbucking die and rod may be relatively rotated to clamp the work article between said work engaging face and said bucking die: and means for applying a force to piQiect the projectible die from the barrel into forming contact with the work article while the work is thus 5. The combination deilned in claim 4 in which said means forI applying a torce to said proiectible die comprises a piston hammer reciprocatvely vmovable within said barrel and pneumatic means Aroi; eiiectingsaid-reciprocative movements. Y `j y with the inner end of the barrel.

10,'1he combination defined in oiaim 9 in' which said `means for applying aforce to said projectibie die comprises a hammer-head on the inner end of said die, a centrally bored piston pneumatic means for effecting said reciprocative movements.

l1. The combination dehned in claim i in which said work engaging face is formed on a separable part of said barrel consisting of a' hotlow cylinder disposed in fluid tight relation'with and concentrically between said projectible die and 'the body of said 'barrel and having' a radially outwardly extending annular iiange between its ends; and in addition thereto p nut threadedlyv engaging the rim surface oi said barrel and formed with a ilangeior engaging said annular ilange to secure said housing.

tible cylinder tothe body of said Jarman.' Huasr. i 

